The invention relates to a device for transmitting torque having at least one disc part fixed directly or indirectly to a crankshaft of an internal combustion engine, and a clutch formed as a structural unit wherein the disc part with the clutch as the structural unit can be fitted on the crankshaft and the structural unit of the clutch can be separated from the disc part for maintenance purposes, and also relates to a method for assembly and maintenance.
A torque transmission device of this kind, described for example in DE PS 44 28 829, can be fitted complete on the crankshaft and has a clutch unit which is connectable to a secondary flywheel mass of a divided flywheel so that for maintenance purposes the divided flywheel can remain on the crankshaft and only the structural unit of the clutch has to be removed.
Dismantling the clutch unit is difficult insofar as for release, screws or rivets fitted from the engine side from outside into the secondary part also have to be removed from the engine side whereby tools have to be inserted in the often very restricted interspace between the engine housing and flywheel and have to be guided in the axial direction through openings in the first flywheel mass part up to the connecting means in order to release individually the numerous connecting means which are spread out round the circumference, resulting in a considerable maintenance expense. In many cases where this interspace is not accessible for the tools this device cannot be used.
The object of the invention is therefore to provide a device for transmitting torque and a corresponding method wherein the worn out parts can be quickly and easily replaced. Furthermore the device is to be capable of use in a wide number of applications and is thus to be more cost-effective since it can be produced in increased numbers. A method for the assembly and maintenance of the device is to be carried out with few steps and using simple tools whereby the clutch can be interchangeable in modular fashion and when required can be replaced by a new clutch module without additional adjustment work.
This is achieved through a device for transmitting torque, more particularly for motor vehicles which has at least one first disc part fixed directly or indirectly on a crankshaft of an internal combustion engine, to which (disc part) a friction clutch is connected which consists as a separate component part of at least a contact pressure plate, a clutch cover which holds axially displaceable and rotationally secured a pressure plate and engages radially round same, and a clutch disc which is mounted axially between the contact pressure plate and the pressure plate and which is fitted with friction linings provided radially on the outside which can be brought into friction engagement with the pressure plate and contact pressure plate by means of at least one energy accumulator acting axially between the pressure plate and clutch cover, and is connectable rotationally secured to a gear input shaft of a transmission on the output side in the force flow, wherein the device can be fitted as a complete unit on the crankshaft and the friction clutch is connected to the disc part by means of fixing means which can be separated from the transmission side.
A friction clutch, for example prefabricated as a module, can be connected to the disc part by means of screws, rivets and/or other fixing means, but a fixing is particularly advantageous having self-locking fixing means so that the clutch during the initial assembly as well as after servicing can be pressed for fixing onto the disc part without the need for tools. Dismantling the clutch is thereby carried out from the transmission side, after the gearbox has been separated from the engine housing, or at least the gear input shaft has been removed from the hub of the clutch disc so that after loosening the connection to the disc part the clutch can be removed. To this end for separating the fixing means the required tools are guided through corresponding recesses in the plate spring tongues which can also serve for fixing the device on the crankshaft and vice versa. It can thereby be particularly advantageous to provide the fixing means or the connection between the disc part and clutch in the radial area of the mountings of the device on the crankshaft, for example radially outside or radially inside same. It is also possible according to the inventive idea to arrange the fixing means directly at the radial height of the hub of the clutch disc so that the tools required for separating the fixing means are guided through corresponding recesses in the hub or through the opening for mounting the gear shaft.
It can thereby be advantageous to use a push-fit connection whereby the two parts are pushed into each other and fixed axially and circumferentially on each other, with at least one or more for example several, circumferentially spaced out push-fit connections forming the connection with the disc part. In the simplest case a push fit connection of this kind can be formed from an axially raised extension arm which is pushed into a corresponding recess of the complementary component part and is held there, for example by means of a fixing screw. It can be particularly advantageous to form the push-fit connection as an axially locking or better still an automatically axially locking snap-fit connection which can be designed so that it can be released in one step.
An advantageous development of a device according to the invention provides axial extension arms of the friction clutch on a second disc part which takes up the contact pressure plate and which is fixedly connected to the clutch cover along its outer circumference. In this way a module can be formed from the clutch which can be removed completely and closed per se from the first disc part through separating the connection at the axial extension arms.
It has proved advantageous to arrange several, for example two to ten, preferably three to six, axial extension arms or mounting points over the circumference of the disc part wherein these are fixedly connected to the same number of axial extension arms of the other disc part or to another component part of the clutch.
In order to form a cost-effective and automatically engaging mechanism, assemblies have also proved advantageous where snap-fit noses are provided on a component part forming the connection to snap-fit in complementary openings of the complementary component part which forms the connection. The snap-fitting noses can thereby be arranged so that all the snap-fitting noses are arranged on one component part, for example on the mountings on the clutch side, or on both mountingsxe2x80x94alternately on the clutch side and engine side, preferably round the circumference. The alignment of the snap-fitting noses can be in any direction wherein an alignment radially outwards has proved advantageous wherein the snap-fitting noses engage in corresponding openings of the complementary component part. In many cases and embodiments it can be advantageous or even a requirement if the disc part fixed on the crankshaft, and the clutch for example are indeed fixed axially through the second disc part which is connected to the clutch cover and engages round the contact pressure plate, but rotatable in the circumferential direction at least over a restricted angular area.
To this end the fastening means, for example circumferentially spaced out extension arms with snap noses, of the one side to be connected can be mounted on a common ring, which can have complementary openings for engaging the snap-fitting noses, of the other side, which is mounted axially fixed and rotatable on one of the two disc parts. In this way the fastening means of the one component part form with the other component part an axially fixed but rotatable connection which can be separated accessible from the gearbox side.
An advantageous development provides a ring which is mounted axially between a disc part, for example the disc part on the clutch side receiving the contact pressure plate, and a component part connected to this disc part and radially overlapping the ring. This component part can have mutually corresponding recesses for the fastening means, for example the snap-fitting noses engaged in the ring, in the region of the proposed relative rotation of the two disc parts. Furthermore the ring can be tensioned axially between this component part and the disc part by means of an axially active energy accumulator so that during relative rotation of the two disc parts opposite one another through the separable connection a rotation of the ring relative to the disc part receiving same likewise takes place with the generation of a friction torque which is fixed for example when using a plate spring as the axial energy accumulator inter alia by its spring constant.
According to an inventive idea the disc part which is mounted on the crankshaft can be formed axially flexible in order to dampen any noises which may arise resulting from the bending vibrations of the crankshaft which can be transferred through the disc part to the drive train.
A further inventive idea proposes the two disc parts rotating circumferentially relative to each other against the action of a damping device having at least one energy accumulator, that is the disc part fixed on the crankshaft is rotatable against the disc part receiving the contact pressure plate preferably over a restricted angular area. The separable connection between the clutch and the disc part on the drive side is produced for example through the snap-fitting connection described above wherein a part of the snap-fitting connection with one disc part is rotatable at least over a restricted angular area opposite the disc part which holds it axially and/or radially fixed, whereby this snap-fitting connection can also provide the bearing of the two parts on each other.
The damping device consisting of at least one circumferentially compressible energy accumulator, for example in the form of at least one coil compression spring which is short compared to the circumference, wherein the ratio between the extension of the at least one energy accumulator and the circumference can be less than 0.5, preferably less than 0.25, or at least a coil compression spring which is long but pre-curved to the installation state, can advantageously be housed in a manner known per se in a chamber formed by a disc part and having corresponding means so that it can be circumferentially biased by the two disc parts. It can be particularly advantageous if the energy accumulator is mounted in a spring cage forming the mounting, which is described in the application DE 198 43 298 and whose contents are to be fully included in the present application, by means of which the at least one energy accumulator can be biased on the drive side and output side. The mounting of two to eight, preferably by four to six, short coil springs acting as energy accumulators can advantageously be in the mounting device and can be installed pretensioned at least on account of the secured fitting and/or can be operated without the addition of lubricants.
It is evident that sets of energy accumulators of this kind need not be restricted to one circumference, but further energy accumulators having the same or different spring rate can be arranged acting between the two disc parts on at least a further radially inner and/or radially outer circumference.
The energy accumulators can advantageously be mounted in the cage-like component part so that one damping module with prefitted energy accumulators is produced which can be installed complete in the device. It can thereby be advantageous to fix the spring cage secured against loss on one of the two disc parts, for example by means of a self-locking device or a snap-fitting connection wherein it can be further advantageous to mount the spring cage on the biasing devices of the disc part. In many cases it can thereby be advantageous to fix the spring cage on the disc part on the drive side and to leave it there when separating the clutch from the disc part on the drive side whereby the clutch module to be exchanged is simpler, lighter and more cost-effective whilst in other cases, particularly when a large amount of wear is expected on the damping device, the spring cage can be fixed on the disc part of the clutch module and can be removed and serviced with the clutch module.
In one proposed embodiment for fixing the spring cage on the disc part on the drive side the fixing means are mounted on the screws for fixing the unit on the crankshaft and have tabs which engage axially round the cage-like component and engage radially in corresponding recesses in the cage-like component part.
In one embodiment for mounting the spring cage on the disc part on the clutch side holding the contact pressure plate, fixing is by means of tabs which are connected to the disc part on the clutch side and engage axially round the cage-like component part and lock radially with corresponding mouldings provided on the side remote from the disc part. The tabs can additionally undertake to bias the energy accumulators on the clutch side.
Where applicable to improve the efficiency of the damping device a friction device can be connected in with the energy accumulators where it acts in the force flow between the disc parts at least over a part of the rotational path of the disc parts opposite one another, the friction device comprising a basic friction which acts continuously during relative rotation of the disc parts, and a friction which is controlled in dependence on the torsional angle.
The basic friction can hereby be produced by a friction disc which is tensioned in the region of the mutual bearing of the two disc parts axially between the two disc parts or between one disc part and a bearing bush which is connected rotationally secured to the other disc part. The axial tension which is required for this purpose can be produced for example by means of the fixing means between the two disc parts, that is through the fixing means of the separable connection between the clutch and the disc part on the drive side.
A further advantageous embodiment proposes a basic friction between the ring which is rotatable opposite the disc part holding same at least in the work area of the damping device for holding the fixing means, and the disc part holding he ring, wherein the ring and disc part can be spaced from each other by means of an axially acting energy accumulator.
Furthermore the basic friction can be produced by means of two biasing devices which are in axial friction engagement, for example two mutually rotatable axially adjoining mounting rings for mounting the energy accumulators of the cage-like component part wherein the biasing devices each adjoin a disc part by their side remote from the friction surface and are thus each tensioned relative to each other by the axially restricted axial connection between the two disc parts.
The controlled friction can thereby take place in that a friction disc engages with keyed connection, more advantageously with backlash, in one of the disc parts and is in direct or indirect friction engagement with the other disc part. The keyed connection can thereby be formed by a spline between the friction disc forming friction engagement with the one disc part, and the other disc part wherein the friction disc can be mounted axially between the two disc parts and for example on the disc part on the crankshaft side.
According to a particularly advantageous further development of the friction control device the friction disc or individual, for example 3 to 9 circumferentially spaced out friction segments are provided on the side of a disc part remote from the damping device, for example on the disc part on the drive side. For this purpose the friction disc can be hung secured against loss by means of axially aligned studs in openings provided in the disc part and running as oblong holes in the circumferential direction, and can be tensioned with the disc part by means of an axially active energy accumulator. The energy accumulator which is advantageously likewise mounted on the outer side of the disc part can in a further advantageous embodiment bias the friction disc from radially outside, whereby it can be supported on a projection of the disc part radially engaging over same or on a component part provided to form a projection of this kind, and can be formed from a plate spring or diaphragm spring. It is obvious that the friction control disc when biased with the axially active energy accumulator can be expanded radially by the studs in order to stabilise the friction control disc in the region of the oblong holes and that in principle an arrangement of this kind can also be advantageous axially between the two disc parts, whereby the axially active energy accumulator can be used on both sides for example as a tensile or compression spring. Furthermore it can be advantageous if the energy accumulator and/or the projection covers the friction control disc so that the latter cannot be contaminated, for example radially from outside.
In one embodiment the component part forming the projection can be formed from a radially inwardly expanded sheet metal folded part which is connected to the disc part and is provided for mounting or forming the starting gear ring which is mounted in the region of the outer circumference of the torque transmission device wherein this folded sheet metal part can additionally contribute to the inertia moment of the disc part on the drive side as a flywheel mass.
The control of the friction control disc lying on the outside is advantageously achieved by providing openings in the studs of the friction control disc through which axially aligned extension arms of the other disc part or of the component part connected thereto can engage with rotational locking and in the proposed friction angular region predetermined by the extension of the oblong hole openings in the circumferential direction turn the friction disc relatively against the one disc part generating a friction moment. It is evident that in many cases the arrangement of a friction disc of this kind can be the disc part on the clutch side and the friction disc can be arranged anywhere over the radius of the device, preferably radially outside, for example for producing longer friction paths, of the damping device, for example radially outside of the spring cage.
In order to achieve a flywheel effect it can be of particular advantage to equip at least one and preferably both disc partsxe2x80x94drive side and/or clutch side disc part holding the contact pressure plate, with a flywheel mass. When equipping both disc parts with a flywheel mass which cannot be disregarded in respect of its inertia mass, the positive effect of a divided flywheel known per se can be achieved.
It is thereby advantageous to form the primary, i.e. drive-side, flywheel mass from the disc part and/or additional material accumulations lying preferably radially on the outside, such as folded sheet metal parts. Flywheel masses of this kind can be formed from one or more folding processes of the corresponding parts wherein these parts can have additionally formed mountings for a starting gear ring and/or markings for the engine management system such as ignition marks, or can form these themselves.
Thus in an advantageous development a folded sheet metal part can be placed on the disc part and both can be shaped radially outwards into a radial flange which has on its outer circumference a spline which is advantageously at least partially hardened, for engagement with the starting motor.
The clutch-side secondary flywheel mass is formed substantially by the parts, such as the contact pressure plate and/or pressure plate as well as clutch cover, forming the friction engagement with the clutch disc wherein the disc part on the clutch side and the clutch disc can make a positive contribution to the inertia moment.
Furthermore according to the idea of the invention it can be advantageous to provide at least on one, preferably on the clutch-side, disc part between the disc part and the flywheel mass a friction clutch which can be restricted in its torsional travel. It can thereby be further advantageous to design the breakaway torque of the friction clutch so that the transferable torque of the friction clutch is less than the maximum torque of the internal combustion engine but greater than the average torque so that torque peaks, for example during the start-up of the internal combustion engine are transferred to the gearbox at least to a reduced extent through the friction moment of the friction clutch. In order to prevent a complete slipping through of the friction clutch, for example in the event of overheated friction linings, the clutch preferably has a restricted rotation capacity so that after a predetermined torsional angle the two relatively rotatable parts are restricted by stops.
An advantageous embodiment has for this purpose a friction clutch on a disc part designed in two parts on the clutch side wherein a flange part forming the bearing for the drive-side disc part is rotatable a restricted amount opposite a flange part holding the clutch with the interposition of the friction clutch where applicable by means of axial stops of the first flange part which engage in recesses of the second flange part corresponding to the torsional angle.
A torque transmission device according to the invention, formed as a divided flywheel with a primary and a secondary disc part provides for the bearing of the two parts on each other a slide bearing, advantageously with the interposition of a slide bearing bush, or a bearing through rolling bearings wherein the slide bearing with a corresponding design, for example with the design of the slide bearing bush with a radial collar which is mounted axially with pretension between the two bearings, can function as a friction device for creating a basic friction.
It can furthermore be advantageous to centre and support the torque transmission device on the crankshaft wherein the disc part on the primary side can be mounted directly on the crankshaft and the second disc part can be mounted on the primary disc part or a bearing flange can be fitted fixed on the crankshaft wherein the bearing for the bearing flange and the rotatable bearing of the second disc part are on different diameters and the primary-side disc part is connected fixedly to the bearing flange. Furthermore one embodiment can be advantageous wherein the bearing of the two disc parts on each other is undertaken by the separable connectionxe2x80x94or viewed from another anglexe2x80x94the common bearing of the disc parts additionally forms the separable connection, for example through the integration of a self-locking device.
Furthermore depending on the type of use it can be advantageous to mount the clutch-side disc part on an outer circumference of the drive-side disc part or bearing flange or to mount the primary disc part or the bearing flange on an outer circumference of the clutch-side disc part. Furthermore from experience of the wear properties of the slide bearing bush the latter can, when separating the two disc parts from each other, thus when removing the clutch by drawing along the second disc part of the divided flywheel, be removed with the clutch-side disc part in order to carry out any required exchange of the slide bearing bush on the clutch module intended for overhauling, or in the case of very wear-resistant bushes to leave these on the primary disc part in order to restrict the number of parts and the weight of the module which is to be overhauled, whereby the bush can be hung or connected secured against loss on the desired disc part, for example through a self-locking device, through connection by means of tabs provided on a disc or bush part connecting with the other component part, by press or shrink fit and/or similar.
According to a further inventive idea the clutch module which can be removed from the device is designed so that a simple separation of the disc part holding the contact pressure plate from the clutch cover is possible, for example by means of a separable connection in the area of the outer circumference of the clutch module in order to allow a quick and easy exchange of the clutch disc which is to be repaired or replaced. For this purpose in one advantageous design the disc part and the clutch cover can be provided with axially aligned sleeve-like attachments which face each other and which axially overlap one another wherein the clutch cover can radially overlap the disc part or the disc part can radially overlap the clutch cover. The axially interfitting attachments are centred on each other and are connected together fixed both axially and circumferentially wherein a free rotating end of one attachment can be welded for example to the other attachment and in the event of maintenance this welded seam or welded points can be separated so that the two parts can be separated.
Another type of separable connection can be for example a separable self-locking connection which fixedly connects the two shoulders axially and circumferentially. One advantageous embodiment can hereby be an undercut section which is provided on one of the two shoulders and which after overcoming the proposed axial overlap of the two shoulders snap fits in the other shoulder. By way of example a restriction can be provided on the inner circumference on the shoulder which fits radially over the second shoulder so that this restriction snap fits into a restriction on the outer circumference of the other shoulder after overcoming an axial overlap for centring the two shoulders. This type of connection can be arranged on the same principle also on the outer circumference of the radially inside shoulder wherein the radius of the shoulder widens out at the free end and after overcoming the overlap is snap-fitted into the inner circumference of the radially outer shoulder which is widened out radially for this purpose.
Separating this closure is by means of a pull-off device or by means of levers which engage through openings provided in the circumference of the two shoulders wherein these openings align in the circumferential direction and axially intersect for applying a lever which is inserted from radially outside through the openings. It is obvious that this lever can also be a part of a pull-off device wherein several levers corresponding for example to the number of the openings can be combined into one pull-off device.
A further advantageous design proposes the use of circumferentially spread out snap-fitting noses set in one shoulder to snap fit in openings spread out correspondingly over the circumference of the other shoulder wherein also here an axial overlap of the two shoulders can be advantageous and the connection can be released through leverage tools in a similar manner to that described above.
For a clutch module which can be replaced as a complete unit it can extremely advantageous according to the invention to design the clutch module so that the clutch can be installed in the torque transmission device or can be replaced in the event of maintenance, whilst set complete, that is with the suitable positioningxe2x80x94operating pointxe2x80x94of the contact pressure plate, clutch cover and pressure plate relative to each other. For this purpose it can be advantageous to make the clutch axially adjustable during the manufacturing process.
For this purpose one design of the invention can provide one or more circumferentially spread out axially deformable stops, for example axially aligned noses shaped round circumferentially at their free end, on the clutch-side disc part or on the clutch cover, for example on one of the two axial shoulders which are brought to adjoin the other component part. In order to adjust the clutch the axial stops are deformed axially until reaching the operating point and the clutch cover is connected rotationally secured and axially fixed to the disc part, for example in the region of the two axial shoulders, for example by welding, staking or by a self-locking device of the type described above. The axially acting force for deforming he stops can thereby be set in dependence on the operating force of the plate spring so that the operating point can be set for example in dependence on the path of the operating force of the clutch.
A further embodiment can provide a thread or bayonet type connection of the two partsxe2x80x94clutch cover and clutch-side disc partxe2x80x94wherein the adjustment of the operating point of the clutch is set by means of an axial path during rotation of the two parts and on reaching the operating point the rotation is stopped and the two parts are secured against further rotation for example by means of a detent mechanism, welding or securing screws.
In a further advantageous embodiment a self-adjusting clutch, such as is known for example from applications DE OS 42 39 291, DE OS 43 06 505 and DE OS 43 22 677, can be integrated into the prefabricated clutch module so that the service or maintenance intervals can be extended.
According to the idea according to the invention a method can also be provided for assembly and or maintenance which particularly in conjunction with the torque transmission device according to the invention can have great advantages over the prior art.
The following method steps and combinations thereof have proved particularly advantageous:
the clutch, at least consisting of at least one disc part, a contact pressure plate, a pressure plate, and a clutch disc, is prefitted as a complete unit;
the at least one disc part is mounted complete on the crankshaft;
in the event of maintenance a part, at least a part of the clutch consisting of a part holding the contact pressure plate, the pressure plate, the clutch cover and a clutch disc is separated from at least one disc part, which is connected to the crankshaft, at a separable self-locking device accessible from the clutch side;
the removed part of the clutch is serviced;
the removed part of the clutch is after servicing connected to the disc part connected to the crankshaft by means of the self locking device.
The method according to the invention can thereby contain a method step which proposes that a dismantled clutch module is not serviced before, but that it can be advantageous to service or replace the part in a workshop set up for this purpose and to fit a corresponding replacement part new on the disc part. A complete compatibility of the clutch unit for this method of procedure can therefore be particularly advantageous.
To renovate the replaced clutch modules it can be advantageous to separate the clutch module on its outer circumference so that the clutch disc is accessible or can be replaced, for example by separating the disc part holding the contact pressure plate from the clutch cover, whereby it can be particularly advantageous to open a separable self-locking device provided at this point by means of a suitable tool. At the end of the maintenance work the connection can be closed again at this point whereby according to an idea of the invention the closure of the clutch module is such that the clutch is reset to its operating point and then the connection is fixed axially and circumferentially.
It is evident that the method also relates to a torque transmission device in the form of a divided flywheel or twin-mass flywheel whose disc part holding the clutch is set indirectly on the crankshaft for rotation to a restricted angular extent on a disc part on the drive side against the action of a damping device wherein the second disc parts can each have a flywheel mass. It can hereby be advantageous to leave the drive-side disc part on the crankshaft in the separation step of the method and to separate the torque transmission device between the first and second disc part. In a few cases it can however also be possible to leave the two disc parts with the damping device on the crankshaft and to separate the clutch module without the disc part.
In the method step where the clutch module is separated from the disc part on the drive side a further method step can involve the servicing of the slide bearing bush which is provided on the bearing of the two disc parts, whereby the slide bearing bush can advantageously be exchanged with the clutch module and can be replaced where necessary. Furthermore in special cases it can be advantageous to leave the slide bearing bush on the drive-side disc part and to replace it in an additional method step when required.
Furthermore it can be advantageous, particularly when producing compatible clutch modules as replacement modules, to provide a method step where the operating point of the clutch is set during the assembly of the clutch cover and disc part on the clutch side, after which the two component parts are fixed axially and circumferentially, for example through welding, staking, an automatic locking device or the like.